<link href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/css/select2.min.css" rel="stylesheet" />
<script src="jquery-1.12.0.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/js/select2.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {
  $(".js-example-basic-single").select2();
});
</script>

<select class="js-example-basic-single">
  <option value="AL">Alabama</option>
    ...
  <option value="WY">Wyoming</option>
</select>
